Compound bows are widely used by archers. The popularity of the compound bow is mainly due to the advantage provided in the reduced pull force required at full draw together with the resulting increase in accuracy. The pull on the bow string is high at the beginning of the draw where the archer at this point is able to exert maximum force. As the draw progresses a little beyond mid-point, there is an over-center action on eccentrically mounted pulleys or cams of the compound bow which decreases the draw force needed to maintain the bow string in the drawn position, while maximizing the energy stored in the limbs of the bow. Thus, at full draw it is relatively easy to hold the arrow and bow string and much easier to perfect aiming technique and proper release resulting in increased accuracy.
A typical compound bow includes one or more eccentrically mounted pulleys or cams pivotably attached relative the bow limbs and serves to support and control the movement of a bow string. Stringing or tuning of compound bows is critical to achieve a proper balance or synchronization of the eccentrically mounted pulleys or cams. The complexity of the stringing and the sensitivity to proper tuning of the bow makes it undesirable to unstring the bow when it is not in use. In some cases it is impossible to string and tune such a bow without the aid of an apparatus commonly known as a bow press.
Since a compound bow cannot be conveniently unstrung and restrung, they are virtually always left in a strung condition. Periodic retuning of compound bows, however, is required to maintain desired performance levels, and to change, replace or repair components of the compound bow, such as the bow string, string sights, dampers, the tension cable, the cams and other components. Through the years a number of bow presses have been developed for facilitating stringing, tuning, and maintenance of compound bows, such as for example, U.S. Pat. Nos. 5,222,473; 5,370,103; 5,433,186; 6,386,190; and 7,185,644.
FIG. 1 illustrates the prior art bow press 200 disclosed in U.S. Pat. No. 5,370,103 (Desselle). Outside surfaces of the limbs 202 of the bow 204 are positioned on outer supports 206. Inner members 208 are engaged with inside surface of riser 210. Drive system 212 moves member 214 in direction 216, causing the limbs to deflect in direction 218. The bow press 200 lacks any specific structure to prevent the bow 204 from moving side-to-side. If the bow 204 is not placed in the press 200 symmetrically with respect to the supports 206, 208, lateral shifting can occur under pressure. If a limb 202 breaks the bow 204 will be ejected from the press 200. With compound bows typically generating forces in excess of 1500 pounds, there is significant danger of damage to the bow and the press and injury to the operator.
If the member 214 is moved too far and the outer support 206 moves past the limb tips 220, the bow 204 to be ejected from the bow press 200. Consequently, the outer supports 206 are typically not located near the bow limb tips. As a result, the bending force applied by the press 200 is concentrated between the outer supports 206 and the riser 210, creating a risk of limb damage.
FIG. 2 illustrates the prior art bow press 250 disclosed in U.S. Pat. No. 7,644,708 (Pittman). Finger assemblies 252 on the bow press 250 are configured to engage with tips of the limbs 254 on the bow 256. Motor 258 displaces the finger assemblies 252 toward and away from each other to deflect the limbs 254. Without any additional restrains on the bow 256, disengagement of one or both of the finger assemblies 252 from the tips of the limbs 254 can result in the bow 256 being ejected from the press 250 in essentially any direction, at very high velocity. If a bow limb breaks the bow press 250 includes no structure to prevent the bow 256 from being launched in a random direction.
The safety concerns surrounding prior art bow presses have increased with changes in limb design. FIG. 3 illustrates a compound bow 270 with parallel or near-parallel limbs 272. The bow 270 includes a long riser 274 and short swept back limbs 272 that are oriented generally parallel. The limb tips 278 are typically past parallel at full draw. The limbs 272 of the bow 270 of FIG. 3 are past parallel 280 even before the string 276 is drawn. In order to remove the tension on the string 276 the limbs 272 must be flexed well past parallel.
Once the limbs 272 are past parallel, there is no structure on the bow press 200 of FIG. 1 preventing the bow 270 from being ejected in the direction 216. In fact, the shape of the limbs 272 encourages the bow 270 move in the direction 216. Past-parallel bows have an even great chance of dislodging from the finger assemblies 252 of the bow press 250. As a result, secondary securing devices, such as straps, are required to secure many modern bows to the bow presses 200 and 250.